A former Great Mills High School social studies teacher acknowledged Monday in court that prosecutors have evidence to support a charge against him of sexually abusing a girl who was in his care.

A judge told Lowell A. Johnson, now 65, of Lexington Park that the charge carries a maximum penalty of 25 years in prison, and that Johnson may remain free on bond while the court awaits the completion of a presentence investigation.

Police were notified last summer, St. Mary’s Assistant State’s Attorney Julie White said during Monday’s plea hearing, of an allegation that Johnson abused the girl when she was 10 years old. The investigation revealed there were four additional victims, the prosecutor said, including one girl who alleged she repeatedly had sexual relations with Johnson.

St. Mary’s detectives filed initial district court charging papers alleging that Johnson engaged in sexual conduct with two children who were in his care as a foster parent, during offenses dating back to 2006. Investigators said that no foster children were living with Johnson when he was arrested last September, and that the two former foster children listed in the charging documents had reached adulthood.

At Monday’s plea hearing, White said that Johnson told detectives that his hand “accidentally” may have penetrated the girl listed in this week’s plea agreement, but that he denied allegations that he had sexual relations with a girl making that claim or that he had any sexual contact whatsoever with three of the girls.

Robert Harvey, Johnson’s lawyer, said at the hearing that his client agrees only that the prosecution’s witnesses would testify about allegations concerning the girl referenced in the plea agreement.

“Mr. Johnson does not admit the conduct outlined here, that those things really happened,” Harvey said.

The school system placed Johnson, a 36-year employee, on leave with pay after his arrest on Sept. 7 last year. At the time a school official said he was entitled to that employment status until the charges against him were resolved in court.

St. Mary’s public schools’ fiscal services and human resources office said Tuesday that Johnson no longer worked for the school system and had not been paid since Sept. 21, 2012.